Most cur­rent weather­iz­a­tion meth­ods tight­en homes’ leaks by 20 to 30 per­cent, said the re­port, but even those num­bers can be im­proved upon. The sav­ings es­tim­ate in the re­port is based on meet­ing the In­ter­na­tion­al En­ergy Con­ser­va­tion Code, which is more achiev­able than some tight­er stand­ards but yields most of the en­ergy-sav­ing res­ults. Meet­ing that stand­ard would re­duce air­flow in res­id­ences by a me­di­an value of 50 per­cent.

The 113 mil­lion homes in the U.S. ac­count for about 23 per­cent of the coun­try’s en­ergy con­sump­tion when their bur­den on the power grid is factored in. The study was fun­ded by the En­ergy De­part­ment, the De­part­ment of Hous­ing and Urb­an De­vel­op­ment, and the Cali­for­nia En­ergy Com­mis­sion.